Historically, the chief method of analyzing trace volatile chemicals (analytes), was solid-phase micro-extraction (SPME) which employs a fiber to collect the analyte and inject it into a gas chromatograph (GC) or liquid chromatograph (LC). This resulted in the capture and injection of only small quantities of the analytes and thus yielded poor sensitivity. It was discovered that if large quantities of vapor or liquid analyte were drawn through a treated sorbent, the components of interest would be concentrated. Solvents were used to selectively remove the analyte from the sorbent and a small portion of the solvent containing the analytes was then injected into the GC or LC. Concentration of the sample via a sorbent was an improvement in sensitivity over straight analyte injection, but it added many processing steps to the analysis, which could increase errors.
Moreover, the environmental impact, chemical composition, concentration trends, and health effects of airborne particulate matter have been extensively studied and described in the literature. Current sampling methods involve the use of gravimetric filters or impact devices, and a wide variety of light and laser scattering devices. Many of the analytical methods for determination of chemical composition of airborne particulate matter require either sophisticated equipment and/or use strict sample preparation techniques. The task of sampling and analysis of airborne particulate matter is often complicated by the complexity of particle size, particle interactions, chemical partitioning between gaseous and particulate phase, and interactions with the sampling media. The health effects of inhaled particulate matter are associated with both the size and shape, as well as chemical toxicity. One of the better known groups of analytes from the latter category is polycyclic aromatic hydrocarbons.
Amongst pollutants, Polycyclic aromatic hydrocarbons (PAHs) have received increased attention in recent years due to their suspected carcinogenic and/or mutagenic nature. PAHs originate in incomplete combustion, and are commonly found in gasoline and diesel motor exhaust, as by-products of open fires, industrial smoke, cigarette and cigar tobacco and smoke. Other sources include coal tar, coal tar pitch, wood preserving agents and coatings, mineral oils, and asphalt. Current most widely used sampling method, solid phase extraction (SPE), for PAHs involve the use of high-volume pumps, filters and sorbent cartridges. These methods require extraction from a filter (or sorbent) with an appropriate solvent, followed by subsequent analysis by HPLC with fluorescence or UV detection, or gas chromatography/mass spectrometry (GC/MS). Many of these methods require considerable sampling expertise and sophisticated sampling equipment, long sample collection and sample preparation time, and strict extraction procedures. Thus, there is a growing demand for faster, simpler and cost-effective sampling for analytical methods for airborne PAHs without compromising low detection limits achievable with some of the conventional methods. In addition, these new techniques should be reusable and environmentally friendly.